title: Influence of sleep apnea severity on blood pressure variability of patients with hypertension.
abstract: OBJECTIVE
  Obstructive sleep apnea (OSA) is a risk factor for the development of hypertension and cardiovascular disease. Apnea overloads the autonomic cardiovascular control system and may influence blood pressure variability, a risk for vascular damage independent of blood pressure levels. This study investigates the hypothesis that blood pressure variability is associated with OSA.
  
  
  METHODS
  In a cross-sectional study, 107 patients with hypertension underwent 24-h ambulatory blood pressure monitoring and level III polysomnography to detect sleep apnea. Pressure variability was assessed by the first derivative of blood pressure over time, the time rate index, and by the standard deviation of blood pressure measurements. The association between the apnea-hypopnea index and blood pressure variability was tested by univariate and multivariate methods.
  
  
  RESULTS
  The 57 patients with apnea were older, had higher blood pressure, and had longer duration of hypertension than the 50 patients without apnea. Patients with apnea-hypopnea index (AHI) ≥ 10 had higher blood pressure variability assessed by the standard deviation than patients with AHI < 10 during sleep (10.4 ± 0.7 versus 8.0 ± 0.7, P = 0.02) after adjustment for age, body mass, and blood pressure. Blood pressure variability assessed by the time rate index presented a trend for association during sleep (P = 0.07). Daytime blood pressure variability was not associated with the severity of sleep apnea.
  
  
  CONCLUSIONS
  Sleep apnea increases nighttime blood pressure variability in patients with hypertension and may be another pathway linking sleep abnormalities to cardiovascular disease.
authors.affiliation: Graduate Program in Medicine: Cardiology, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Steinhorst
authors.forename: Sandro C
authors.initials: SC
authors.lastname: Gonçalves
authors.forename: Ana T
authors.initials: AT
authors.lastname: Oliveira
authors.forename: Daniela
authors.initials: D
authors.lastname: Massierer
authors.forename: Miguel
authors.initials: M
authors.lastname: Gus
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Fuchs
authors.forename: Leila B
authors.initials: LB
authors.lastname: Moreira
authors.forename: Denis
authors.initials: D
authors.lastname: Martinez
authors.forename: Flávio D
authors.initials: FD
authors.lastname: Fuchs
mesh_terms: D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D002319:Cardiovascular System / Q000294:innervation; D002940:Circadian Rhythm / Q000502:physiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology*